1. Field of the Invention
The present invention relates in general to a marine propulsion system, and more particularly to a shifting mechanism for an outboard drive.
2. Description of Related Art
Many forms of outboard drives employ forward, neutral, reverse transmissions. Such transmissions are common in both outboard motors and in the outboard drive units of inboard-outboard motors. These transmissions typically include a driving bevel gear and a pair of oppositely rotating driven bevel gears that are journaled within a lower unit of the outboard drive. A dog clutch mechanism selectively couples a propeller shaft to one of the driven bevel gears to rotate the propeller shaft in either a forward or a reverse direction, or to disconnect the propeller shaft from the driven gears in a neutral position. When the propulsion drive includes a second propeller, a second dog clutch selectively couples a second propeller shaft to one of the driven bevel gears. These gear sets, dog clutch mechanisms and associated shifting linkage are typically located in the lower unit of the outboard drive, below a water line of the watercraft. U.S. Pat. No. 4,793,773 to Kinouchin et al. discloses an example of this type of propulsion unit transmission.
In an effort to minimize the size of the lower unit and to provide a parabolically shaped lower unit, others have located the forward, neutral, reverse transmission on a vertical propulsion axle of the motor. U.S. Pat. No. 4,343,612, issued to Blanchard, discloses an example of an outboard unit with the transmission located on the propulsion axle of the motor. The outboard unit of Blanchard includes an input shaft and a drive shaft, which are positioned with portions of each juxtaposed. A plurality of meshed gears are used to couple the juxtaposed portions of the input shaft and the drive shaft together. An elaborate rim-type clutch is used to selectively couple the drive shaft to one of the gears driven by the input shaft. Although this shifting mechanism couples the drive and input shafts together, the numerous gears and complicated shifting mechanism significantly increase the size of the forward, neutral, reverse transmission, as well as increase the cost off the outboard drive.